What Are the Best Metrics to Measure Changes in Body Composition?

February 10, 2019

by Cathe Friedrich

When you’re trying to lose weight or change your physique, you need metrics to know how well you’re meeting your body composition goals. There are a variety of ways to chart your progress from stepping on a scale to whipping out a tape measure and taking measurements. Each method has its pros and cons. What are the body composition metrics you can use and which are best for seeing whether you’re meeting your physique goals?

The Scale

The bathroom scale is the way most people monitor their progress. Guys and gals who are trying to shed pounds step on it once a day or once per week and record the number. But a standard bathroom scale gives incomplete information and it can cause you to reach inaccurate conclusions. If you gained weight, it could be water weight, weight from the big meal you just ate, body fat, or muscle. You may be up a pound or two because you’re constipated! We tend to be too obsessed with the number on the scale and this can lead to unhealthy eating habits.

A standard scale is the worst way to monitor your body composition, mostly because it says little about the composition of your body weight. If you use a scale, at least standardize your weigh-ins. Weight first thing in the morning after a trip to the bathroom. Expect your weight to rise throughout the day due to the food and beverages you eat. A heavy meal, particularly one high in salt, can cause a sharp rise in your weight and it can take several days for it to return to baseline. But most of the weight is due to water retention and topping off your glycogen stores. Glycogen holds onto water and causes an increase in body weight.

A Body Fat Percentage Scale

Body fat percentage is a better metric for following body composition than total body weight. The most accurate ways to measure it, like Dual-Energy X-ray Absorptiometry (DXA) and hydrostatic weighing, require a trip to a center that offers these services and it can be expensive.

You also can buy a body fat percentage scale that estimates body fat percentage at home. These scales use bioelectrical impedance, a method that sends a weak electrical current through your foot to measure body fat percentage. The scales aren’t always accurate, but you can improve their accuracy by taking a few precautions. Always weigh first thing in the morning after urinating and drinking a cup of water. Even mild dehydration can throw the reading off. Make sure your feet are dry when you step on the scale for a weigh-in. The reading they give you may be off a bit, but you can use the scale to see if your body fat percentage is changing over time, as long as you take the precautions mentioned.

You can also use skin calipers. This simple, low-tech gadget is reasonably accurate if you use good technique. However, taking the measurements is somewhat time-consuming, as you have to measure at several sites, and this method is more dependent on user technique than stepping on a scale.

A Tape Measure

A tape measure is a good metric for determining how your health risk is changing over time. Studies show that waist size is a better indicator of future health risks, including cardiovascular disease and type 2 diabetes than body mass index. A large waist size is a marker of greater visceral fat, deep abdominal fat that produces inflammatory chemicals that increase the risk of health problems like cardiovascular disease and type 2 diabetes. If you’re a female, a waist size larger than 35 inches is high risk. Another way to look at it is your waist measurement should be no more than half your height. The best way to measure your waist size is to place the tape measure just above your hip bones and breathe out before recording the number.

Waist size is an excellent measurement to follow as the circumference of your waist says a lot about your future health risks and how much visceral fat you carry. It’s a metric we all should track.

How Your Clothes Fit

Some people don’t like to step on a scale of any type. Instead, they monitor how their clothes fit and feel. The best way to do this is to take a few pieces that you don’t wear often and place them in the back of your closet. After not wearing them for a month, put them on and see if they feel lose or tight. Using this method can help you avoid being tied to a scale but it’s not very precise. Plus, it’s a delayed indicator. If you only put on the items once per month and they’re tight, you could have reacted quicker had you known you were gaining weight earlier.

Photographs

Some people say that seeing a photograph of themselves looking overweight was the kick in the butt they needed to get off the couch and start exercising. But, like how your clothes fit, photographs aren’t a quantitative metric that gives you qualitative information. You might decide you like or don’t like how you look based on a photograph, but you won’t get information about body fat percentage and waist circumference that says something about your health risks. This isn’t the best metric to use as it really isn’t a metric.

The Bottom Line

What method do you use? Don’t become too fixated on numbers, but it’s a good idea to follow your waist circumference over time, as this is a marker for health risk. Also, consider getting a body fat percentage scale and follow your body fat percentage over time. Remember, it’s not as accurate as a DXA scan or hydrostatic weighing but you can use it to follow changes in body fat percentage over time. If you only use a bathroom scale, don’t be too fixated on the numbers. Too many factors other than a rise in body fat can cause you to weight more on a given day.

References:

NIH National Heart, Lung, and Blood Institute. “Assessing Your Weight and Health Risk”
Journal of the American Heart Association. March 6, 2018. Vol 7, Issue 5.